DE2949545A1 - CATALYST AND METHOD FOR PRODUCING METHACRYLIC ACID - Google Patents

Description

The invention relates to a method for producing methacrylic acid by oxidation of methacrolein, which is characterized by the application of a new catalyst that has a high Activity, high selectivity and a very long catalyst life.

The invention also relates to the Katalsaytor.

It is true that various catalyst systems have recently been used for the catalytic oxidation of methacrolein in the vapor phase recommended, however, the oxidation of methacrolein in contrast to the oxidation of acrolein has been used to produce acrylic acid not yet implemented in industrial practice. It can be assumed that the difficulty is that the yield of the end product is not as high as in the manufacture of acrylic acid and the life of most of them Catalytic converters is too short to have a stable catalytic effect

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maintaining viability for a long period of time, etc.

Most of the catalysts recommended for the catalytic oxidation of methacrolein in the vapor phase are around those with molybdenum-phosphorus as the main component and structurally they are regarded as phosphomolybdates, for example mainly as the ammonium or alkali salts of heteropoly acids thereof.

The main disadvantage of these catalysts is their short catalyst life , and decomposition of the structure of the heteropoly acid salt occurs slowly during the long reaction operation and, in the X-ray diffraction analysis, crystal growth of MoO. ,, that with the decrease in catalytic Activity. Accordingly, such catalysts do not have a long enough life for industrial use Application to and to maintain the catalytic activity of such catalytic systems over a longer period of time, it is inevitable, under the circumstances, to use extremely mild reaction conditions that are far from economic needs are.

U.S. Patent 3,875,220 and U.S. Patent 4,001,316 describe a catalyst for the oxidation of methacrolein. However, they are methacrylic acid yields are not good in the examples of these patents.

In addition, DE-OS 27 39 779 Mo-P-V-Al-Y-O catalysts (where Y is not mandatory and represents Cu, etc.) with heteropolyacid structure used for the oxidation of methacrolein. This catalyst is stable. The yield of methacrylic acid in this publication is large, but not sufficient . DE-OS 28 47 288

relates to Mo-P-V-Cu-Z-O catalysts (where Z

is not mandatory and represents tin etc.) with a heteropolyacid structure and a method for producing methacrylic acid

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by oxidation of methacrolein in the presence of the catalyst.

This catalyst has a high activity and a high selectivity. In addition, this is a catalyst very stable and therefore has a very long catalyst life.

According to the invention, the above catalyst is to be further improved will. It is possible with the catalyst according to the invention. Methacrylic acid from methacrolein in high yield and stable State for a long time.

The invention relates to a method for producing methacrylic acid by oxidation of methacrolein with molecular oxygen or a gas containing molecular oxygen in the vapor phase, which is characterized in that a catalyst with a heteropolyacid structure of the general formula

Mo V. P Cu, As X-O abc d efg

used, wherein Mo, V, P, Cu, As and O each represent molybdenum, vanadium, phosphorus, copper, arsenic and oxygen, X one or more elements selected from the group of tin, lead, cerium, cobalt, iron, zirconium , Thorium, Tungsten, Germanium, Nickel, Rhenium, Wisrauth, Antimony, Chromium, Boron, Magnesium, Silver, Aluminum, Zinc and Titanium and a, b, c, d, e, f and g mean the atomic ratio of the elements, where

a = 10,

b = a number of 3 or less than 3, with the exception of O and

preferably from 0.5 to 2, c = a number from 0.5 to 6 and preferably from 0.5 to 3,

d = a number of 3 or less than 3, with the exception of 0 and

preferably from 0.01 to 1.0,

e = a number of 3 or less than 3, with the exception of 0 and

preferably from 0.01 to 1.0,

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f = a number from 0 to 3 and preferably from 0 to 1.0, g = a number, determined as a function of the valency and the atomic ratio of the other elements, and usually represents a number from 32 to 90.

The invention also relates to the catalyst defined above.

A particularly preferred component X comprises tin, thorium, cerium, Tungsten, germanium, rhenium, bismuth, antimony, boron and aluminum.

The above catalyst used in the present invention contains different elements and has a heteropolyacid structure as indicated by the characteristic peaks of X-ray diffraction at 2Θ = 8.0 °, 8.9 °, 9.3 °, and the like. The basic structure of the catalytic converter is doing Phosphovanadomolybdic acid, however, is believed to have other incorporated elements contributing to the catalytic improvements Effectiveness and selectivity as well as contribute to the stability of the structure through partial replacement of the element components in phosphovanadomolybdic acid and incorporation into the structure of heteropoly acid.

The catalyst according to the invention is water-soluble because it is like described above, has a heteropolyacid structure. It can also contain components that are insoluble in water, like oxides of the constituent elements, but they have no significant effect on the performance of the invention Catalyst on.

It is believed that, as in the usual case, the inventive The catalyst is also in the reduced form under the reaction conditions by reduction with the feed gas containing methacrolein at an early stage of the reaction. The reduced form can also be obtained by using reducible starting materials for the elemental

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2943545

constituents of the catalyst, with the addition of the reducing agent during production of the catalyst or by treatment of the catalyst with a reducible gas or reducing gas.

The catalyst according to the invention is extremely suitable for industrial use, as it has a high level of effectiveness, high selectivity and a very long catalyst life having. In addition, according to the invention, the reaction can be carried out at a high space flow rate, since the increase in space velocity does not have a significant effect on the results of the reaction when applied of the catalyst according to the invention. The catalyst according to the invention is water-soluble, which has additional advantages because it can be easily worn and regenerated by a wearer, and also easily re-immersed in water after deactivation can be solved during a long period of use for implementation.

The catalyst according to the invention can by general methods for the production of common heteropolyacids, but care should be taken to prevent the formation of a heteropolyacid ammonium salt structure to avoid in the resulting catalyst.

The catalyst of the present invention can be, for example, as follows getting produced. The catalyst of the present invention can be prepared by reacting the starting materials of Element building blocks in water or in an organic solvent, conversion of the reaction product into the corresponding one Acid, if it is the ammonium salt, extracting the reaction product if necessary and evaporating to dryness. The conversion of the ammonium salt into the corresponding acid can be carried out in a customary manner, for example by Extraction with ether from an acidic aqueous solution, by ion exchange processes and the like. The extraction of the reaction product can be carried out using a suitable

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Neten organic solvent, such as ether.

Particularly preferred manufacturing methods include such as dispersing or dissolving the starting material, for example the oxides or phosphates of the elemental building blocks in water, their reaction with heating, while optionally hydrogen peroxide is added, removing the insoluble component, if necessary, and then evaporating the solvent to dryness, or the reaction of phosphovanadomolybdic acid with oxides, phosphates, sulfates and the like. From other elemental components.

Various substances can be used as starting materials for the element building blocks of the catalyst, provided that they are used in the treatment in such a process to a catalyst with a heteropolyacid structure, but not with an ammonium salt structure to lead.

The starting materials that can be used for the molybdenum component include, for example, molybdenum trioxide, molybdic acid or their salt, heteromolybdic acid or its salts, molybdenum metal and the like.

The raw materials that can be used for the phosphorus building block include orthophosphoric acid, phosphorous acid, hypophosphorous acid and their salts, diphosphorus pentoxide and the like.

The raw materials usable for the vanadium component include vanadium pentoxide, vanadium oxalate, vanadium sulfate, vanadic acid or their salts, vanadium metal and the like.

The raw materials that can be used for the copper component include copper oxide, copper phosphate, copper sulfate, copper nitrate, Copper molybdate, copper metal and the like.

The starting materials that can be used for the arsenic component

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include arsenic oxide, ortho arsenic acid, meta arsenic acid, pyro arsenic acid and their salts and the like.

The starting materials usable for the component X include corresponding oxides, phosphates, nitrates, sulfates, carbonates, Molybdates, metals of the elements X and the like.

It is true that the catalyst according to the invention produces one as such high catalytic activity, however, can have preferable effects such as the improvement of the thermal stability and the Catalyst life, as well as the increase in the yield of methacrylic acid can be expected by application to a suitable carrier. Preferred carriers include silicon carbide, aluminum powder, Diatomaceous earth, titanium oxide, oC aluminum oxide, etc. The active carriers that react with the heteropoly acid are not preferred.

The calcination process that is required in most cases is not necessary when preparing the catalyst of the present invention. Therefore, the catalyst of the present invention can can be easily manufactured, and the cost of the catalyst can be reduced.

The reaction components used for the oxidation reaction according to the invention are methacrolein and molecular oxygen or a molecular oxygen-containing gas wherein the molar ratio of oxygen to methacrolein is preferred from 0.5 to 10 and particularly preferably from 2 to 5.

Preferably, water vapor is added to the feed gas in an amount of from 1 to 20, and preferably from 2 to 15, based on the molar ratio based on methacrolein, too.

The feed gas can also contain other inert gases, for example nitrogen, carbon dioxide, saturated hydrocarbons and the like. The by catalytic oxidation of

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Isobutylene or tert-butanol obtained ¹ methacrolein-containing gaseous effluent can be used as feed gas.

The reaction temperature is preferably from 200 to 380 C and particularly preferably from 250 to 350 C.

The amount of the feed gas is preferably 100 to 5,000 hours, and more preferably 500 to 3,000 hours. as space flow rate (SV), based on the NTP standard. Since the increase in the space velocity (SV) has no significant effect on the reaction results when the catalyst according to the invention is used, the Reaction can be carried out at a high space velocity.

The implementation according to the invention can be carried out at any pressure may be carried out above or below atmospheric pressure, but it will generally be conveniently carried out at a pressure close to carried out at atmospheric pressure. The preferred pressure for the reaction according to the invention is 0.9 8 to 4.9 bar (1-5 atm.)

The reaction according to the invention can be carried out in any desired type of reactor, such as the fixed bed type, the fluidized bed type or the moving bed type will.

The following examples do not specifically focus on oxygen details referred to in the catalyst composition as this is determined by the atomic ratio and valence of the other Determine elements.

The conversion of methacrolein, the yield of methacrylic acid and the selectivity for methacrylic acid are defined as follows:

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Conversion of methacrolein (%)

- converted methacrolein (mol) ..__ added methacrolein (mol)

Methacrylic Acid Yield (%)

_ resulting methacrylic acid (mol) _1Of) added methacrolein (mol)

Selectivity for methacrylic acid (%)

_ Yield of methacrylic acid. Conversion of methacrolein

example 1

100 grams of molybdenum trioxide, 6.3 grams of vanadium pentoxide, 1.1 grams of copper oxide, 8.0 grams of orthophosphoric acid, and 1.8 grams of pyroarsenic acid were dispersed or dissolved in 1000 ml of deionized water. The resulting mixture was brought to the boil and refluxed with stirring for about 6 hours to give a clear orange-red solution. It was evaporated to dryness on a hot bath. The dried product (catalyst) obtained in this way had a composition of Mo ₁ ^ V ₁ P ₁ Cu- ~ AS _ and was found by observing the diffraction peaks at 2Θ = 8.0 °, 8.9 °, 9.3 ° and the like. by X-ray diffraction, as a heteropoly acid. It was ground to 0.297-0.71 mm (24-48 mesh) and then placed in a tubular Pyrex glass reactor 18 mm in internal diameter and the reactor immersed in a fluidized bath. The feed gas with a composition of methacrolein: oxygen: nitrogen! Water vapor = 1: 2.5: 14: 7 (as a molar ratio) was passed through the tubular reactor

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SV = 1,600 hours ¹ (NTP standard) passed, and subjected to the oxidation reaction at a reaction stone temperature of 320 ° C. for 120 days. The results are given in Table I.

After the reaction time of 120 days, an X-ray diffraction analysis was carried out of the catalyst and it was confirmed that no molybdenum trioxide was formed and that the Structure of the catalyst had not changed.

Example 2

100 g of molybdenum trioxide , 6.3 g of vanadium pentoxide, 1.1 g of copper oxide, 8.0 g of orthophosphoric acid, 1.8 g of pyroarsenic acid and 2.1 g of tin oxide were used as the starting material for the preparation of the dried product (catalyst):

Ko ₁ "VP ₁ Cu ,. .As _no Sn _n _ 10 11 0.2 0.2 0.2

in the same procedure as in Example 1 used. The dried products obtained in this way were confirmed by examining the diffraction peaks at 2Θ = 8.0 °, 8.9 °, 9.3 and the like. by X-ray diffraction, as a heteropoly acid.

It became a continuous reaction for 30 days using the above catalyst among the same Reaction conditions carried out as in Example 1. The results are shown in Table I.

After 30 days of reaction, the X-ray diffraction analysis showed of the catalyst that the structure of the catalyst

had not changed.

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Examples 3-21

The 2.1 g of tin oxide of Example 2 were in each of the examples by 3.2 g of tri-lead tetroxide, 2.4 g of cerium oxide, 1.1 g of tricobalt tetroxide, 1.1 g of iron oxide, 1.7 g of zirconium oxide, 3.7 g thorium oxide, 3.2 g tungsten trioxide, 1.5 g germanium oxide, 1.0 g nickel oxide, 3.4 g rhenium heptoxide, 3.2 g bismuth oxide, 2.0 g antimony trioxide, 1.4 g chromium trioxide, 0.9 g boric acid, 0.6 g of magnesium oxide, 1.6 g of silver oxide, 0.7 g of aluminum oxide, 1.1 g of zinc oxide and 1.1 g of titanium oxide were replaced, and dried products with the compositions shown in Table I were obtained. The dried products obtained in this way were confirmed by diffraction peaks at 2Θ = 8.0 °, 8.9 °, 9
diffraction as a heteropoly acid.

oeaks at 2Θ = 8.0, 8.9, 9.3 and the like by X-ray

: \ s was using a series of continuous reactions of the above catalysts under the same reaction conditions as in Example 1, carried out. The results are listed in Table I.

After 30 days of reaction, the X-ray diffraction analysis carried out on the catalysts confirmed that the Structure of the catalyst had not changed.

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T a b e 1 1 e

composition

Strö React

mation-

time temp.

(Days) ( ⁰ C)

Conversion of

Methacrolein (%)

Selectivity for methacrylic acid

Yield of methacrylic acid

1 " ⁰ IoVi ⁰ V ₂ ^ ₂ 1
120 320
320 93.4
93.5 83.6
83.9 78.1
78.4 2 ^Mo 10 ^V l ^P * i ^Cu 0.2 ^As 0. ₂ ^Sn 0. ₂ 1
30th 320
320 91.2
92.1 83.9
83.3 76.5
76.7 3 ^Mo 10 ^V l ^P l ^Cu 0.2 ^As 0.2 ^Pb 0. ₂ 1
30th 330
330 90.4
91.2 82.2
83.3 74.3
76.7 4th ¹¹⁰ WVi ⁰ V Λ. 2 ⁰⁸ 0.2 1
30th ^! 315
315 92.5
92.2 81.5
81.8 75.4
75.4 5 ^Mo 10Vl ^Cu 0. ₂ ^A8 0.2 ^Co 0.2 1
30th 312
312 95.7
96.0 80.9
80.8 77.4
77.6 6th "" ΐΟνΛ ^ Ο.Σ ^ Ο.Ζ 1
30th 315
315 94.1
94.7 82.1
82.1 77.3
77.7 7th ¹¹⁰ IoVi ⁰ V ₂ ^ ₂ ² V ₂ 1
30th 317
317 93.8
93.1 83.7
83.9 78.5
78.1 8th 1
30th 32p
320 92.2
92.8 82.4
82.1 76.0
76.2

Tabel

(Continuation)

example

Catalyst composition

Strö React

mation-

time temp.

(Days) ( ⁰ C)

Conversion of
Methacrolein (%)

Selective yield did for meth- an methacrylic acid acrylic acid

9 " ⁰ IoVl ⁰ V 2 ^As 0.2 ^W 0.2 1
30th 325
325 90.4
90.1 83.7
84.0 75.7
75.7 10 1
30th 320
320 92.0
92.7 82.8
82.6 76.2
76.6 11 " ⁰ IOV1 ⁰¹¹ 0.2 ^As 0.2 ^Ni 0.2 1
30th 320
320 94.9
94.4 82.7
83.4 78.5
78.7 12th "° loVl ° ^u O. 2 ^ 0.2 ** 0.2 1
30th i 320
¹ 320 94.1
93.7 80.5
81.1 75.8
76.0 13th ^Ko 10 ^V l ^P l ^Cu 0.2 ^As 0.2 ^Bi 0.2 1
30th 320
320 96.0
95.5 81.3
81.7 - 78.0
78.0 14th " ⁰ IoVl ^ O. 2 ^ 0.2 ^ 0.2 1
30th 330
330 90.9
91.5 84.0
83.8 76.4
76.7 15th " ⁰ IOVl ⁰¹¹ 0.2 ^A8 0.2 ^Cr 0.2 1
30th 320
320 91.3
90.6 83.6
83.3 76.3
75.5 16 ¹¹⁰ IOVl ⁰¹¹ 0.2 ^A8 0.2 ^B 0.2 1
. 30th 320
320 89.9
90.3 83.7
83.1 75.2
75.0

(Jl ul

T a b e 1 1 e

(Continuation)

example

Catalyst composition

Strö React

mation-

time temp.

(Days) ( ⁰ C)

Conversion Selective! Yield

mentation of act for meth- to meth-

Methacro-acrylic acid acrylic acid linen (%) (%) (%)

17th ^Mo 10 ^V l ^P l ^Cu 0.2 ^ 0.2 ^ 0.2 1
30th 320
320 92.4
92.3 83.4
83.7 77.1
77.3 18th ^Mo 10Vl ^Cu 0.2 ^As 0.2 ^A S ₀ .2 1
30th 330
330 95.3
95.4 81.4 ■
81.7 77.6
77.9 19th ^{> I0} 10 ^V 1 ^P 1 ^CU 0.2 ^AS 0.2 ^M 0.2 1
30th 330
330 92.7
91.9 83.0
83.0 76.9
76.3 20th ^M ° 10 ^V l ^P l ^Cu 0.2 ^As 0.2 ^Zn 0.2 1
30th ' 320
■ ' 320 91.4
92.1 82.7
82.8 75.6
76.3 21 V ₁ ^ o ₁ A ₁₂ ¹¹ O .: 1
30th 330
330 93.3
92.9 80.9
81.6 75.5
75.8

-fr-CD

Examples 22-25

The dried products shown in Table II are prepared as in Example 1 and it was confirmed by X-ray diffraction analysis that they were heteropoly acids.

Under the same reaction conditions as in Example 1, continuous reactions were carried out using the above Catalysts carried out. The results are shown in Table II.

After 30 days of reaction, X-ray diffraction analysis was carried out the catalysts carried out. It was confirmed that the structure of the catalysts had not changed.

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T a fa e 1 1 e

Γ I

Example catalyst

^c composition

Strö React

mation-

time temp.

(Days) ( ⁰ C)

Conversion Selective! Yield

mentation of act for meth- to meth-

Methacro-acrylic acid acrylic acid linen (%) (%) (%)

22nd ¹¹⁰ IOVl ⁰¹¹ 0.2 ^As 0.2 ^Sn 0.1 ^Pb 0.1 ' 1
30th UJ UJ
NJ NJ
O O 93.4
92.8 82.4
82.9 77.0
76.9 23 ^to 10Vl ^Cu 0.2 ^A3 0.2 ^Ge 0.1 ^Ni 0.1 1
30th 320
320 94.0
93.9 83.1
83.3 78.1
78.2 24 1
30th 320
320 94.8
94.8 81.1
81.6 76.7
77.4 25th 1
30th "320
'320 92.9
93.6 80.8
81.0 75.1
75.8

Examples 26-31

The dried products of Table III were as in the example 1 and they were confirmed by X-ray diffraction analysis as heteropoly acids.

Using the above catalysts were continuous Reactions carried out under the same reaction conditions as in Example 1. The results are in the Table III listed.

After 30 days of reaction, the X-ray diffraction analysis showed of the catalysts that their structure had not changed.

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T a b e 1 1 e

I I I

Ex. ^Ka talysator-

^c composition

Stream React Conversion mungs functional ment of Time temp. Methacro (Days) ( ⁵ O leash (%)

Selective yield

did acrylic acid for methacrylic acid

O O IO

26th ^Mo 10 ^V 1.5 ^P l ^Cu 0.3 ^As 0.1 1
30th 345
345 91.3
92.0 80.1
80.3 73.1
73.9 27 ^ ioWVs ^ o.i ^ o.i 1
30th 340
340 87.1
87.0 75.5
75.6 65.8
65.8 28 ^Mo io ^v o.5 ^p i ^c Vo5 ^As o.05 ^Sn o.2 1
30th 320
320 90.0
89.8 75.8
75.6 68.2
67.9 29 " ⁰ IO ⁷ L ₅ ¹ V *!. 0 ^ 0.2 ^N1 0.2 1
30th ι · 330
· '330 91.4
90.2 78.4
77.7 71.7
70.1 30th ¹¹⁰ IOVz ⁰¹ O. 2 ^ 0. Λ. Ο 1
30th 335
335 92.7
92.3 80.5
81.0 74.6
74.8 31 ^M ° 10 ^V l ^P 0.5 ^Cu 0.3 ^As 1.0 ^Ge 0.5 1
30th 340
340 87.5
87.8 79.9
79.2 69.9
69.5

Examples 32-33

Using the catalyst of Example 6, the oxidation was carried out of methacrolein carried out in the same way as in Example 1, but with the space flow rate (SV) has been changed. The results are shown in Table IV. These results show that the increase in space velocity (SV) had no significant effect on the reaction results.

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Tab 1 le ' T V

Example catalyst

^c composition

SV

React

(Std ' ¹ ) "onstemp. ( ⁸ C)

Conversion selection privilege from tat for methacrolein methacrylic - (%) acid C%)

Yield to

Methacrylic acid (%)

32 ^M ° 10Vl ^Cu 0.2 ^As 0.2 ^Fe 0.2 800
* 290 94.2 82.2 77.4 33
t ^Mo 10 ^V l ^P l ^Cu 0.2 ^ 0.2 ^ 0.2 3600 335 93.8 81.7 76.6

N) CO • Γ »

Comparative experiment 1

A 28% aqueous ammonium hydroxide solution was added to the clear orange-red solution obtained in Example 1 (pH * 1.0), added to adjust the pH to 5.3. After the solution was evaporated to dryness, the dried product was 0.297 0.71 mm (24 - 48 mesh) and in the air for 8 hours Calcined at 38O ° C. The catalyst obtained had the composition:

on, and the formation of the. Ammonium salt of heteropolyacid confirmed by X-ray diffraction and IR absorption spectrum. It was taking the same continuous reaction Use of the above catalyst carried out. The results are shown in Table V.

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Tab 1 1 e

O ο 3Y CJ δ ο ζ ο ■ " to ζ cn U)
TJ m O CJ m OI ο

Comparative catalyst test composition

Strö React

mation-

time temp.

(Days) ( ⁰ C)

Conversion selectivity yield

mentation of act for meth- to meth-

Methacroacrylic acid acrylic acid
lein (%) (%) (%)

1 320 ■ 90.1 82.1 74.0 15th 320 77.8 76.2 59.3 (NH ₄ ) _{1 # 5} y ^ ₁₀ V ₁ P ₁ Cu ₀₂ As _0i2

Claims (8)

Claims 1. Catalyst with heteropolyacid structure and the general formula ^Mo a ^V b ^P c ^Cu d ^AS e ^X f ° g where Mo, V, P, Cu, As and O are each molybdenum, vandin, phosphorus, copper, arsenic and oxygen, X is one or more of the elements selected from the group of tin, lead, cerium, cobalt, iron, zircon, Represents thorium, tungsten, germanium, nickel, rhenium, bismuth, antimony, chromium, boron, magnesium, silver, aluminum, zinc and titanium and a, b, c, d _f e, f and g represent the atomic ratio of the elements, where a = 1O, b = a number of 3 or less than 3, excluding 0 , c = a number from 0.5 to 6, d = a number of 3 or less than 3, excluding 0, e = a number of 3 or less than 3, excluding 0, f = a number from 0 to 3, g = a number that is determined by the valence and that Atomic ratio of the other elements. 030026/0736 2. Catalyst according to claim 1, wherein a = 10, b = a number from 0.5 to 2, c = a number from 0.5 to 3, d = a number from 0.01 to 1.0, e = one Number from 0.01 to 1.0, f = a number from 0 to 1.0. 3. Catalyst according to claim 1, wherein X is one or more of the Elements selected from the group of tin, thorium, cerium, tungsten, germanium, rhenium, bismuth, antimony, boron and aluminum means. 4. Process for the production of methacrylic acid by the oxidation of methacrolein with molecular oxygen or a molecular one Oxygen-containing gas in the vapor phase, characterized in that a catalyst with a Heteropoly acid structure and general formula Mo V, P Cu, As Χ, Ό abc d efg used, where Mo, V, P, Cu, As and 0 each mean molybdenum, vanadium, phosphorus, copper, arsenic and oxygen, X one or more of the elements selected from the group of tin, lead, cerium, cobalt, iron, Represents zircon, thorium, tungsten, germanium, nickel, rhenium, bismuth, antimony, chromium, boron, magnesium, silver, aluminum, zinc and titanium, and a, b, c, d, e, f and g mean the atomic ratio of the elements , whereby a = 10, b = an integer of 3 or less than 3, with the exception of 0, c = a number from 0.5 to 6, d = an integer of 3 or less than 3, with the exception of O, 030026/0736 e = a number of 3 or less than '3, excluding 0, f = a number from 0 to 3, g = a number that is determined by the valence and the atomic ratio of the other elements. 5. The method according to claim 4, characterized in that a catalyst is used in which a = 10, b = a number of 0.5 to 2, c = a number from 0.5 to 3, d = a number from 0.01 to 1.0, e = a number from 0.01 to 1.0, f = a number from 0 to 1.0. 6. The method according to claim 4, characterized in that a catalyst is used in which X is one or more of the Elements selected from the group of tin, thorium, cerium, tungsten, germanium, rhenium, bismuth, antimony, boron and aluminum represents. 7. The method according to claim 4, characterized in that one works at a reaction temperature of 200 to 380 ° C. 8. The method according to claim 4, characterized in that the reaction is carried out in the presence of steam. 030026 / 073S